Do you have any actual evidence that Singer did that just to piss off Marvel, because I have yet to see any? If you don't, then don't even go there. The script for DOFP was finished LONG before the AOU writing even began. I've seen nothing to indicate that this wasn't always Singer's intention, just people jumping to conclusions.

Agree 100%. It's a totally biased way of thinking. Singer announced Evan Peters as Quicksilver like what? One week after Whedon? Not only the script was ready months before that but they had already started filming for six weeks. And in that week they sat down decided to put Quicksilver in just to "spite Marvel", rewrote the script to include him and found an actor to portray him. Really? Seriously that's not how movie business work. Is it an absolutely impossible scenario? I guess stranger things have happened. But is it the most logical assumption? Definitely not. Both studios probably sat down and discussed this long before we found out about it. The rest is just foolish talk and prejudice.